Light control sheet

Abstract

A light control sheet includes a light control layer including an organic polymer layer including voids and a liquid crystal composition filling the voids, transparent electrode layers, and transparent support layers. The liquid crystal composition includes a liquid crystal compound and a dichroic dye, the light control layer is sandwiched between the transparent electrode layers, the light control layer and the transparent electrode layers are sandwiched between the transparent support layers, the light control sheet switches from a transparent state to an opaque state exhibiting a first color due to change in alignment of the liquid crystal compound and the dichroic dye in response to change in potential difference between the transparent electrode layers, and a parallel light transmittance PTa in the opaque state and a parallel light transmittance PTb in the transparent state satisfy a relationship PTb/PTa>80.

The invention claimed is: 
     
         1 . A light control sheet, comprising
 a light control layer comprising an organic polymer layer having voids and a liquid crystal composition filling the voids;   a plurality of transparent electrode layers formed such that the light control layer is sandwiched between the transparent electrode layers; and   a plurality of transparent support layers formed such that the light control layer and the transparent electrode layers are sandwiched between the transparent support layers,   wherein the light control layer is formed such that the liquid crystal composition includes a liquid crystal compound and a dichroic dye, the transparent electrode layers are configured to change potential difference between the transparent electrode layers such that the light control layer switches from a transparent state to an opaque state exhibiting a first color due to change in alignment of the liquid crystal compound and the dichroic dye, and the light control layer includes the liquid crystal compound and the dichroic dye such that a parallel light transmittance PTa in the opaque state and a parallel light transmittance PTb in the transparent state satisfy a relationship PTb/PTa>80.   
     
     
         2 . The light control sheet according to  claim 1 , wherein the parallel light transmittance PTa in the opaque state is 0.6 or less. 
     
     
         3 . The light control sheet according to  claim 2 , wherein a total light transmittance in the opaque state is 30% or less. 
     
     
         4 . The light control sheet according to  claim 3 , wherein each of a chromaticity a* and a chromaticity b* in a CIE 1976 (L*a*b*) color system according to JIS-Z-8781-4 is in a range of −15 to 15 in the opaque state. 
     
     
         5 . The light control sheet according to  claim 4 , wherein the light control layer includes spacers that exhibit the first color. 
     
     
         6 . The light control sheet according to  claim 3 , wherein the light control layer includes spacers that exhibit the first color. 
     
     
         7 . The light control sheet according to  claim 3 , further comprising:
 a colored layer that exhibits the first color,   wherein each of the transparent support layers has a first surface and a second surface facing away from the first surface such that the first surface is contacting a respective one of the transparent electrode layers and that the colored layer is formed on the second surface of at least one of the transparent support layers.   
     
     
         8 . The light control sheet according to  claim 2 , wherein each of a chromaticity a* and a chromaticity b* in a CIE 1976 (L*a*b*) color system according to JIS-Z-8781-4 is in a range of −15 to 15 in the opaque state. 
     
     
         9 . The light control sheet according to  claim 2 , wherein the light control layer includes spacers that exhibit the first color. 
     
     
         10 . The light control sheet according to  claim 2 , further comprising:
 a colored layer that exhibits the first color,   wherein each of the transparent support layers has a first surface and a second surface facing away from the first surface such that the first surface is contacting a respective one of the transparent electrode layers and that the colored layer is formed on the second surface of at least one of the transparent support layers.   
     
     
         11 . The light control sheet according to  claim 1 , wherein a total light transmittance in the opaque state is 30% or less. 
     
     
         12 . The light control sheet according to  claim 11 , wherein each of a chromaticity a* and a chromaticity b* in a CIE 1976 (L*a*b*) color system according to JIS-Z-8781-4 is in a range of −15 to 15 in the opaque state. 
     
     
         13 . The light control sheet according to  claim 11 , wherein the light control layer includes spacers that exhibit the first color. 
     
     
         14 . The light control sheet according to  claim 11 , further comprising:
 a colored layer that exhibits the first color,   wherein each of the transparent support layers has a first surface and a second surface facing away from the first surface such that the first surface is contacting a respective one of the transparent electrode layers and that the colored layer is formed on the second surface of at least one of the transparent support layers.   
     
     
         15 . The light control sheet according to  claim 1 , wherein each of a chromaticity a* and a chromaticity b* in a CIE 1976 (L*a*b*) color system according to JIS-Z-8781-4 is in a range of −15 to 15 in the opaque state. 
     
     
         16 . The light control sheet according to  claim 15 , wherein the light control layer includes spacers that exhibit the first color. 
     
     
         17 . The light control sheet according to  claim 15 , further comprising:
 a colored layer that exhibits the first color,   wherein each of the transparent support layers has a first surface and a second surface facing away from the first surface such that the first surface is contacting a respective one of the transparent electrode layers and that the colored layer is formed on the second surface of at least one of the transparent support layers.   
     
     
         18 . The light control sheet according to  claim 1 , wherein the light control layer includes spacers that exhibit the first color. 
     
     
         19 . The light control sheet according to  claim 18 , further comprising:
 a colored layer that exhibits the first color,   wherein each of the transparent support layers has a first surface and a second surface facing away from the first surface such that the first surface is contacting a respective one of the transparent electrode layers and that the colored layer is formed on the second surface of at least one of the transparent support layers.   
     
     
         20 . The light control sheet according to  claim 1 , further comprising:
 a colored layer that exhibits the first color,   wherein each of the transparent support layers has a first surface and a second surface facing away from the first surface such that the first surface is contacting a respective one of the transparent electrode layers and that the colored layer is formed on the second surface of at least one of the transparent support layers.